JPH04501978A - Method for purifying acids from substances containing acids and salts - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] and a voice and 4. or “nono”.

1 The present invention relates to a method for separating acids from acid-containing salt solutions. More specifically, the present invention contains a bipolar till (bipolar ■embrane) and an anion membrane A new use of the device for the separation of acids from solutions containing acids and salts.

By electrodialysis in two compartment cells Water separation is well known.

For example, U.S. Patent No. 4,391,680 discloses a three-compartment moisture Discloses the formation of strongly acidified sodium chloride and aqueous sodium hydroxide solution by separation. There is. Three-compartment electrodialysis water separation devices are well known in the art. Alternating acid, salt and base compartments These devices consist of alternating bipolar, anion and cation exchange membranes that form It is shown. U.S. Application No. 135,562 uses electrodialysis equipment to concentrate acids. Then, the salt was removed by an electrodialysis three-compartment water separator (water-splHter). discloses the recovery of acids from materials containing acids and salts, consisting of separating the acids from Ru.

U.S. Patent No. 4,608.141 discloses a multi-chamber two-compartment electrodialysis water separation device and the same device. discloses a method for basification of water-soluble salts using . U.S. Patent No. 4,536.269 discloses a multi-chamber two-compartment electrodialysis water separation device and the same device. discloses a method for acidifying water-soluble salts using These two patents are in the second category. The use of dialysis water separation devices and their salt treatment is discussed.

Take out the base solution from the base compartment of one three-compartment water separator and transfer it to the second three-compartment water separator. of two conventional three-compartment electrodialysis water separators feeding through the base compartment of the separator. Staging is known. Attempts to improve the efficiency of bipolar membranes No. 3,111,472 [Oda et al.] describes three-compartment electrodialysis. Placing a microporous water-permeable cationic or neutral membrane in the acid and/or base compartment of the water separation device Discloses that.

Bipolar membranes are often useful for water separation by electrodialysis to obtain acids and bases. It has been known for many years [Oda et al. U.S. Pat. No. 2.289.095, Chianda ( U.S. Pat. No. 3,787,304 to Chianda et al.; U.S. Pat. No. 4,552,635], various cell shapes Although their use has been reported [Japan Patent No. 2923 ('5 No. 8), reported in Chemical Abstracts 53: 11070b; U.S. Patent No. 4,536.269 and U.S. Pat. No. 4.608.141], effectively H4 or or) - Transports only ions and does not form incompatible products (purification of acids) Their use as highly selective membranes, which are effective for .

None of the above references use bipolar membranes in devices such as three-compartment separators. Also, the separation of the acid-containing salt solution and subsequent removal of the salt solution is not disclosed.

Prior art, such as U.S. Pat. No. 4,536,269, shows that cation membranes The selection of hydrogen ions over other cations, such as metal ions, other than hydrogen ions. Although it has been shown to preferentially enable selective transport, this selectivity is small.

Kohoza Pact The present invention uses an aqueous feed stream containing an acid and a salt. This is a method of separating acid from The salt contains a cation and an anion. is at least one bipolar layer consisting of a cation layer and an anion layer. It is carried out using acid purification equipment that includes membranes. The cation layer allows cations to pass through and negative The ionic layer allows anions to pass through. The cation layer is a barrier against anions. The anion layer is a barrier to cations. Each bipolar membrane has at least one the first anionic membrane and the at least one second anionic membrane. acid The acid purification unit consists of at least two It has two compartments (co+partment). The supply compartment is a bipolar membrane anion. the space between the anion layer and the at least one first anion membrane; defined. The product compartment includes a cation layer of a bipolar membrane and at least one second anion. defined as the space between the membrane and the membrane. The equipment used is a three-compartment water separator (tw o Compartment water 5plitter) has the same structure. However, the functionality is completely different.

The method includes an aqueous feed stream containing an acid and a salt in at least one feed co. the aqueous product feed stream, including the step of feeding the aqueous product feed stream to the also feeds one product compartment.

Applying a sufficient potential to create a direct current across the device causes hydrogen to form in the bipolar membrane. Ions (Ho) are introduced into the product compartment. This current carries at least one anion. Pass through two anion membranes. Anions enter at least one product compartment.

The concentration of acid in the feed compartment is due to anion migration. The introduction of Ho increases the acid concentration in the product compartment. This method is Additionally, the step of removing product from the product compartment and the production feed from the feed compartment including the extraction process.

The apparatus includes at least one feed compartment, each feed compartment intersects with a product compartment. In a preferred embodiment, the device comprises a plurality of alternating bipolar membranes. and an anionic membrane, resulting in a plurality of product compartments and feed compartments. like this The arrangement compacts manufacturing equipment, thereby reducing capital and space requirements let

In an alternative embodiment of the method of the invention, the device further comprises at least one anion. a permselective layer and at least one anion membrane; The acid compartment includes at least one cationic membrane between the anionic and cationic layers of the bipolar membrane. 0, defined as the space between the ionic membrane used in this embodiment of the invention. A device in which the feed stream forms a complex (co-ρ1ex) with the anion layer of a bipolar membrane. containing metal ions that adhere to the bipolar membrane by forming insoluble hydroxides or by forming insoluble hydroxides. Particularly useful. The device used has the same structure as a three-compartment water separator, but with 8 1st ability is completely different.

Another embodiment of the invention provides a step of supplying a solution containing a salt and an acid to a three-compartment acid purification apparatus. This is a method that includes In a three-compartment acid purifier, a solution of salt and acid produces a first salt stream.

Substantially all of the acid is separated from this first salt stream. The second section of the folic acid refining equipment is salt-pickled p. Preferably, this first acid stream is produced such that l+ is about 7; the acid is distributed between the three compartments. Exits the acid purifier as the 1M stream. The acid present in the first salt solution is then processed A substantially neutral first salt stream removed from the water is fed to a three-compartment water separation device. salt is separated to produce a second base stream, a second acid stream comprising an acid and optionally a salt, and finally a dilute salting stream. Forms a dilute residue of the salt compartment. In certain preferred implementations, dilute salt pickling reconcentrate for recirculation. Dilute salting can be done using suitable methods, including electrodialysis or reverse osmosis. It can be concentrated by any suitable means.

Three-compartment acid purification system and three-compartment water solution for the production of acids from salt solutions containing varying amounts of acid The combination with a decomposition device reduces the membrane area and power requirements of a three-compartment device compared to a three-compartment device. It is advantageous because of the small amount. Some additional operational freedom is also obtained, e.g. Salting can be fed into the salt compartment of a three-compartment water splitter, and this equipment Because of its strong properties, a weak base type membrane can be used. Such membranes possess high efficiency. do.

Diagram] F x ku single L” v Takumi Figure 1 shows a prior art device having only a monopolar membrane and which can be used for the purification of acids. Or indicate a cell.

Figure 2 shows an apparatus using a bipolar membrane that can be used to purify acids according to the method of the invention. location or cell.

FIG. 3 shows conceptual details of a bipolar membrane during operation according to the method of the invention.

FIG. 4 depicts another embodiment of the invention useful for purification of highly contaminated acids.

FIG. 5 shows a schematic diagram of an apparatus used in an embodiment of the invention.

FIG. 6 shows a flow diagram of an apparatus useful in the method of the present invention.

Figure 7 is a graph of time vs. current efficiency [η (%)], time vs. supply concentration, and product concentration. It is.

FIG. 8 is a schematic diagram of an apparatus used in another embodiment of the invention.

Figure 9 shows a particular implementation of the invention in which the current contains cations that do not form insoluble hydroxides. A schematic flowchart of apJ is shown.

FIG. 10 shows a particular implementation of the invention in which the current involves cations forming insoluble hydroxides. 1 shows a schematic flow diagram of an embodiment.

Hatsudara Omega Segasa Theory Dish The invention will be understood by those skilled in the art upon reference to the accompanying drawings.

The present invention provides an aqueous feed stream comprising an acid and a salt consisting of metal cations and anions. This is a method for separating acids. This method consists of a cation layer and an anion layer. It is carried out in a device containing at least one bipolar membrane. Each bipolar membrane has at least Disposed between one first anion membrane and at least one second anion membrane.

A feed material zone is provided between the anion layer of the bipolar membrane and the at least one first anion membrane. There are product components. Bipolar membrane cation A product compartment exists between the anion layer and the at least one second anionic membrane.

The method provides an aqueous feed stream containing acids and salts to at least one feed compartment. and supplying an aqueous product stream to at least one product compartment. , providing a sufficient electrical potential to generate a direct current through the feed compartment and the product compartment. Then, H formed by a bipolar membrane is introduced into the product compartment. Anion layer of bipolar membrane Or, water moves into the cation layer and separates, and the hydroxyl moves through the anion layer. It is believed that the hydrogen ions migrate through the cation layer. Hydrogen ions are It is transported through the cation layer to the product compartment. Fewer anions from the feed stream Both pass through one anion membrane to the product compartment. Acid concentration in feed compartment The degree is that anions move into the product compartment and combine with hydrogen ions formed in the bipolar membrane. and as a result of producing acid. The product stream containing # is removed from the product compartment This resulting feed stream, containing salts and depleted in acid anions and hydrogen ions, is It is removed from the feed material compartment. Certain preferred embodiments are described below with reference to the accompanying drawings. and explain.

FIG. 1 is a prior art device, also referred to as a "cell," useful in the purification of acids. Preceding technique The surgical cell 10 consists of alternating cationic membranes 12 and anionic membranes 14. Direct current as an electrode, The entire cell is supplied by an anode 16 and a cathode 16. Anion membrane and cation membrane The intervening space is a substantially closed compartment, except for the inlet and outlet. anion The membrane allows the anion AA11- (n is an integer) with an n- charge to pass through, but it does not allow the positive ion to pass through. Prevents the passage of ions. Although the cation membrane allows hydrogen ions to pass through, Designed to resist the passage of cations, such as metal cations expressed as The zero dotted line indicates that a small amount of metal cations leak from the cation membrane. Cation membranes have high hydrogen ion mobility (■ability), so other Hydrogen ions are generally selectively passed compared to cations.

a feed stream comprising a salt and an acid consisting of cations such as metal cations and anions; is fed to feedstock section F. In feed compartment F, the anion membrane approaches the anode. However, since the cation membrane is close to the cathode, hydrogen ions and other cations are The anions are driven in the opposite direction through the anion membrane.

The compartment adjacent to the feed compartment is called the product compartment P. The product compartment P has an inlet and It is a closed compartment with an exit. The product compartment has a cation membrane close to the anode and a cathode close to it. It exists between the anion membrane and the anion membrane. Therefore, hydrogen ions moving toward the cathode and other positive The ions stop when they reach the anion membrane 14. Anions move towards the anode, It stops when it reaches the cation membrane. A product stream, typically an aqueous stream, enters the product compartment P. Supplied. The transfer of hydrogen ions and anions to the product compartment P by direct current is The product stream is removed from the anionic membrane along with the acid and H. The feed material being withdrawn, including other cations carried in, did not migrate, initially (original 5alt) and some acids.

Although the illustrated prior art cell is capable of separating acid from salt, the purity of the resulting acid is a relatively low, thin layer of anion exchanger, especially when attempting to extract most of the acid. Cation membranes containing catalytic substances improve the selectivity of cation membranes for monovalent cations. [K, Shimasaki et al., J.A. Pull, Poly, Sci, (J, Appl, Poly, Scj,), 34.1093 (1987)), such membranes are more effective in separating polyvalent cations from acids. However, significant metal cation transport still occurs and H.

and other monovalent cations. Not effective.

FIG. 2 illustrates a device, or cell, useful in the present invention. This device is at least FIG. 3 shows a schematic diagram of a bipolar membrane, including one bipolar membrane 20, where the bipolar membrane has positive polarity. The cation layer includes an on layer 22 and an anion layer 24, and the cation layer contains, for example, hydrogen ions. Manufactured from materials that allow cations to pass through. The anion layer is, for example, hydroxyl Allows anions such as on to pass through. The anion and cation layers also allow water to pass through. . At the boundary between the anion layer and the cation layer, hydrogen ions and Droxyl ions are formed. With sufficient potential applied across the layer, a positive Movement of charged hydrogen ions toward the cathode through the cation layer and negatively charged hydrogen Migration of the xyl anion through the anion-selective membrane towards the anode occurs.

In a preferred embodiment of the invention, as shown in Part 2, the bipolar membrane 20 is It exists between the on membrane 30 and the second anion membrane 32. Anion layer 24 of bipolar membrane A feed compartment F is present between and the at least one first anionic membrane 30 .

between the cation layer 24 of the bipolar membrane and the at least one second anion 1Ei32. There is a product compartment P. Cation layer 22 faces cathode 22 .

By the method of the invention, acids and e.g. metal cations or ammonium cations can be an aqueous feed stream 34 containing cations such as supply Aqueous product stream 36 is fed to product compartment P. Aqueous product stream 36 is an acid and soluble salts. The direct current introduced by electrodes 26 and 28 flows into the feed material compartment. F and the product compartment P, and the hydrogen ions formed in the bipolar membrane are transferred to the product compartment P. This current introduced into the membrane causes the anion A''- to pass through the anion permselective membrane.

The acid concentration in the feed compartment consists of anions and net hydrogen ions. n1on) decreases as a result of being transferred to the product compartment. The resulting product stream 3 6' is removed from the product compartment and the resulting treated feed stream 34' is removed from the feed compartment. taken from.

According to the method of the invention, the device further includes a plurality of alternating bipolar and anionic membranes. containing at least one feedstock compartment, each feedstock compartment producing one product compartment. Alternate with painting.

Since bipolar membranes can exclude the movement of almost all cations except H, the resulting acid contains much less salt (i.e., cationic impurities) than the feed stream. On includes monovalent, divalent and trivalent metal cations and non-metallic cations including ammonium. Anions include -valent anions, such as halides (41alides). divalent anions, e.g. sulfate, trivalent anions, e.g. phosphate. Typical acid-salt combinations that can be purified, including valent anions and mixtures thereof The combination is HCI/NaCl, acetic acid/Na0Ac, HCI/N) + 4CII Na zSOn/HtSOat RtSOn/FeSO4/Fe*(SO=js.

NaNOs/)INO31NHaNOs/HNOs+ NazPOa/HsPO a+HNOx/N1(NOsn!+NBFa/Cr(Be4)z.

There is HtSOa/Cu5Oa+ or l(F/KF. Mixtures of acids also have cationic impurities. For example, HF/HNO2/Ni(NO3) can be treated and purified to obtain IIF/HNO.

Many metals are combined with anions such as chloride or fluoride, e.g. FeClm - and TiFh-. Where these ions exist If the The acid will contain metal impurities. However, using a cationic membrane instead of a bipolar membrane cationic metal contaminants are transported across the cationic membrane. Purity is higher than purity.

The acid feed stream can have an acid concentration ranging from O, IN to 5N or more, but generally High concentrations can be obtained with weak acids (acids that ionize poorly). The concentration of the product is Usually higher than the concentration of the feed material, but especially if the concentration of the feed material is high, the produced The product concentration may be less than the feed material concentration. Effect of the 1# type system shown in Figure 2 The rate depends on the selectivity of the anionic membrane. A good anion membrane allows the generation of high acid concentrations. make it possible.

The acid concentration in the feed is preferably between 0.5N and 5N, most preferably between 1 and 3N. It is N.

The salt can be at concentrations up to saturation, but concentrations from o, oo molar to saturation are preferred. Typically, the amount is 0.1 mole or more.

The resulting product stream 36' has a salt concentration less than 0.1 times that of the initial feed fL34, preferably Preferably, the salt concentration can be 0.01 times or less.

Useful working temperatures from 0°C to 100°C, if membrane stability and solution component solubility permit. becomes possible. In general, membrane life is longer at low temperatures, and power consumption is lower at high temperatures. The lower the temperature, the preferable working temperature is 25 to 60°C, and the more preferable working temperature is 35°C. ~50°C. In the case of sulfuric acid, temperatures above 45°C are most preferred.

Unlike prior art coated cation membranes that only contain a thin coating of anion exchange material. , the bipolar membranes useful in the present invention are highly selective for the transport of anions. Such membranes containing a significant thickness of exchange material are described in U.S. Pat. No. 4,024,043. No. 4,116.889 [Ch. Landa et al.] and U.S. Patent No. 4.584.246 [Lfu et al.] It is stated in Anion exchange membranes are based solely on charge number or ion size. Rather, Donnan Principle (El, E) Tch, shirt y-(L”, 5haffer) and M, Nis, Mintz (M, S, Mintz)'s Principle of Desalination s of Desalination) Chapter 6 “Electrodialysis (El electrodialysis) J% Academic Press (＾cadem ic Press), NY (1966), Kay, Nis, Svigler ( K., S., Spieglar (eds.)] to eliminate cations. Therefore, anion exchange membranes are generally highly selective, and remove all cations regardless of the number of charges. Conceptually, the high selectivity of bipolar membranes for He, which is effective for This is achieved as illustrated in the figure. Due to Donnan's exclusion principle, cations (H ”) are excluded from the anion layer. Ho is an anion as part of the neutral water molecule. can pass through the main layer. Water molecules exchange cations with the anion exchange layer of the bipolar membrane. It can be ionized into H and Ol+- at the boundary between the exchange layer and the membrane. It is transported according to the potential gradient. O' generated at the interface is inside the anion layer of the membrane or reacts with P just outside the anion layer.

The net result is an almost exclusive movement of 2' across the membrane.

Pickling containing certain acids, such as stainless steel pickling The stream contains a relatively small amount of acid that can form complexes with the anion layer of the bipolar membrane Can form soluble hydroxides. For such a flow, additional normal cations Using a cell arrangement as shown in Figure 4 containing the membrane, the anion layer of the bipolar membrane is Can tear damage against.

In the method using the apparatus shown in FIG. 4, an anion layer 24 and at least one anion At least one cationic membrane 38 is present between the ion layer and the ion layer. Anion in a bipolar membrane Between the layer and the cationic membrane there is an acid compartment A. Feed stream 40 has an anion layer and Metallic compounds that can form complexes or form insoluble hydroxides that adhere to dipolar films. Aqueous acid stream 42 is fed to the product compartment, and aqueous acid stream 44 is fed to acid compartment A. be provided.

The operation of the device shown in FIG. It is similar to the device shown in FIG. 2 and was described above in connection with FIG. Acid compartment is bipolar Acts as a barrier to reduce metal ion concentration near the anionic surface of the membrane .

The purpose of the anion layer is to utilize the selectivity of the cation membrane for H ion transfer to The goal is to reduce the metal ion concentration near the anionic surface of the polar membrane. Cation membrane and The acid supplied to the acid compartment A formed by the bipolar membrane is produced from the feed compartment. It can be part of a product. The ratio of P to metal ions transported across the cation membrane is , in the feed, especially when the metal is present as a neutral or anionic complex. It should be higher than that. # Metal ion concentration in the compartment is lower than in the feed compartment can be maintained. *The acid from the compartment is removed from the feed stream after it has been sufficiently contaminated with metals. supplied inside. Although there is no loss in acid recovery, the efficiency of the process is reduced.

Processing the salt-contaminated current in the prior art apparatus of FIG. 1 and producing the product of this apparatus as shown in FIG. Essentially the same effect can be achieved by introducing it as a feed into the device of the invention shown in You can get results. The use of a single device as shown in Figure 4 is advantageous due to its simplicity and reduced number of membranes. Reducing equipment requirements, including lower power consumption and pumping capacity II ing cap-a ic ty) to reduce operational requirements. more advantageous.

Figure 9 shows the electrolytes containing metal cations or ammonium that do not form insoluble hydroxides. A product compartment in which the stream was processed in a three compartment acid purifier 50 of the type shown in FIG. Substantially all of the acid can be recovered from. Reference numbers in Figures 2 and 9 are the same. Common to all elements. Stream 34' resulting from feed stream F is substantially neutral. This neutralized stream 34' containing salts of 34' is processed into a three-compartment or three-compartment water splitter! processed with The base and additional acid can then be recovered. As shown in Figure 5, three sections With the water splitter 60, complete recovery is achieved. This kind of three-compartment water splitting system The location is disclosed in related U.S. Pat. No. 4,740,281 by reference. . i of the dilute salt layer from the water splitter! Optionally, a compression means 70 is provided to convert the salt into a recirculating stream. 72 to the salt section WiS of the water splitter. The concentration means Electrodialysis cells (ED cells) such as those described in U.S. Pat. No. 4,740,281. outperforms prior art methods that require neutralization of the salt layer with the product base, including , the main advantage of such a process is that it replaces carrying out the entire process in a three-compartment device. In addition, part of the process is performed in a three-compartment system, which reduces the total membrane area and total power consumption. , since no aqueous base is added, the dilute base effluent from the water splitter is reduced. Ru. The embodiment shown in FIG. It can be used for manufacturing MCI.

FIG. 10 shows a particular preferred embodiment of the invention in which cations forming insoluble hydroxides are present. A preferred embodiment will be described. Prevents metal hydroxide from adhering to the anion side of the bipolar membrane. Some acidity is required to stop the acid recovery. You can't do it all.

Similar to the implementation example shown in Figure 9, reference numbers in Figures 2 and 6 refer to common elements. It is common. The resulting feed stream 34' is treated to remove insoluble hydroxides. Ru.

In FIG. 10, feed stream 34' is fed to a neutralizer/filter 80. In FIG. flow 34' is a neutralizer/filter 8 for a water-soluble aqueous base stream 82 containing salt and dilute acid; Supply to 0.

An insoluble base is formed and is filtered off and removed from the insoluble base line 84. During ~ The aqueous salt fL86 of the hydrated water-soluble salt is prepared in a three-compartment water splitter, such as a three-compartment water splitter 8B. Or it can be fed into a three compartment water splitter. This is an acid, salt and base stream90. 92 and 82, respectively. Base stream 82 is recycled to neutralizer/filter 80. make a circle Salt layer 92 is concentrated as described with respect to concentration means 70 in FIG. Can be done. Some dilution of the salt stream to be treated occurs and the majority of the process is carried out in a three-compartment unit. neutralization, but it retains some advantages over direct neutralization.

Examples of particularly useful bipolar membranes include U.S. Patent No. 2.829.095 to Oda et al. U.S. Pat. No. 4.024.043 (single film bipolar and U.S. Pat. No. 4,116,889 (cast) II. The most preferred are bipolar membranes. but , if there is a means that can separate water into hydrogen and hydroxyl ions, e.g. such as spaced anionic and cationic membranes in which water is present. Any means can be used.

Useful cationic membranes employed are moderately acidic [e.g. containing nicgroups] or strongly acidic [e.g. c group) cation permselective The membrane exhibits low resistance at the operating pH. A particularly useful cation membrane is Du Pant's Nafion (Naf 1on) ■110 and 324 positive There is an ionic membrane. A further preferred cationic membrane is a commonly distributed one such as Clapp et al. , of the composition and structure described in U.S. Pat. No. 4,738.764.

Useful anionic membranes used include strongly, moderately or mildly basic anions. It is a membrane. Examples of membranes that can be used include Ionics+Inc. (Watertown, Massachusetts) from [Ionics ) Sold as 204-UZL-386 anion membrane] or Asahi Glass Industry (^ From 5ahi Glass Co.) [Product name, Selemion ) @AMν, AAV, ASV sold as anion permselective membrane], commercial available at.

The current that normally passes through the water splitter (@ater 3plitter) is Specified by design and performance characteristics readily known to those skilled in the art and/or subject to routine implementation. It is a direct current with a voltage determined by experiment. 25-300amp, / square footage A current density of 28 to 33 (1on IHamp, /d) is preferable, and ~150 amp,/sq ft (55-165 milHamp,/d) current For certain applications where higher or lower current densities are particularly preferred, higher or lower current densities may be used. Degrees can also be used.

Periodically interrupting the iit flow, preferably for 0.5 to 5 minutes, particularly preferably for 1 to 3 minutes contamination of the anion layer of the bipolar membrane [i.e. metal ions] It is beneficial to reduce the effects of ion complexation and metal hydroxide deposition. Such an interruption The interval and period of time depends on the relative amounts of acid and metal and the fluid flow rate in the cell (fluid fl o+*). Effective periods and intervals can be determined by experiment.

The increase in pressure required to maintain the flow rate through the feed compartment interrupts the current , the current is reduced to normal until this high pressure returns to normal level. ) is one of the signs that it should not be increased.

In electrodialysis and related processes, the flow rate through the stack is The input rate of the fresh feed material is generally greater than the stack is operated in a recirculating format, with the recirculating feed being sent to a recirculating tank (recycle tank). servoir). In this way, favorable compositional changes of the entire system can be obtained. Measure the net input rate so that U@ However, the concentration change in one pass through the stack is Small, continuous feeding and product withdrawal to each recirculation loop in the system (steady state operations) or periodically (batch operations).

Regarding acid purification, it is not necessarily necessary to recover the acid as an acid, but rather to recover the acid as an acid. It can also be converted into products. For example, containing HtSOa/Cr□(SOa)s. The acid product stream was treated with Ca(OH)z to give a ratio of Relatively harmless gypsum waste can be formed. take out the acid The treatment of the remaining Cr-containing stream produced only a small amount of hazardous Cr-containing waste. , or Cr recovery can be made simple.

Other useful bases for neutralizing acids include, but are not limited to, NaOH, K Oh.

There are NH and OH.

The following examples provide a detailed explanation of the invention. It should not be construed as limiting to what is obvious to a person skilled in the art from what is shown. .

In the example, the current efficiency (η, eta) is equal to the mass balance (mass balance) e), i.e. the H content change in the feed and/or product is Judgment was made from changes in amount and concentration. Titrate to pH 5 with H concentration standard Na0HN solution It was measured by The recirculation tank should be flushed so that the volume can be read. I marked it with kale. The formula for calculating current efficiency is as follows: current efficiency - raw bottom H゛moles obtained in the product or lost from the feed material tens of cells x electric 1 (A) x hours time (seconds) +96,500 (cou11 moles)] Efficiency is determined over a certain period of time (the t is enterval) and the cumulative efficiency from the start of the experiment (c (uws+eta). Stack voltage includes the potential required for electrode reaction. is the total supply potential (measured by a high impedance voltmeter), the metal concentration is the atomic Atomic absorption (AA) or inductively coupled argon Plasma (indnctivity coupled argon plas ma) Measured by (ICAP) spectroscopy.

Above The electrodialysis stack described in FIGS. 5 and 6 was assembled. The stack is a PT anode, From bipolar membrane, 4 sets of alternating anion exchange membranes and bipolar membrane and stainless steel cathode forming an anode compartment, four sets of alternating product compartments and feed compartments, and a cathode compartment. It was something to do. Each layer has a regular hexagonal shape and an area of 23d, They were separated by a space of 1.25 Bm. According to U.S. Patent No. 4.766.161 The bipolar membranes prepared by Ta. The anionic membrane was Asahi Glass AAV from Asahi Glass. Anode and cathode compartments was supplied by a pump not shown in FIG. 6 from a tank containing 0.5 Mg acid.

Regarding Figure 6, the initial feed solution (impure acid) (50) is Fe″″280 ppm, 4.7ON including Mn” 290pp- and A1” 3200pp- 251 sulfuric acid (such feed material is similar to the composition of the spent A1 anodizing bath). ), the product tank (pure acid) (52) was equipped with 0.4N sulfuric acid 2501d. I entered. The solution from the tank is pumped by pumps M1 and A2 at a rate of more than 100 mL/min. into the recirculation loop at threshold speed and into pumps P1 and P2 through a section of the stack. Therefore, it was circulated at a rate of about 500 L/min. Excess introduced into the recirculation loop The solution was returned to the tank.

A DC current of 2.5 A was passed for a total of 336.5 minutes to circulate the solution through the cell. Under experiment The acid concentration in the feedstock (Eq.) and the product concentration (C=.) are determined by The final product is 3.651i sulfuric acid and 263* L, containing 1.3g of Fe, 1.3g of Mn, and 6.71g of AI. Ta. The final feed solution was 0.56N sulfuric acid with a volume of 177*L, Fe 266 ppm, Mn 309 ppm, and Al 3285 ppm. Supplement Approximately 90% of the acid originally present in the feed was recovered and 0.7% of A1 was added to the product. It was just a transition.

■-1 Purification of sulfuric acid, the equipment was the same as that used in Example 1, but in this case the feed material 42ppm of Cd'', 221ppm of Fe'' and asppm of Ca''''. The product was charged with 315 mL of 4.51N sulfuric acid, and the product was charged with 301 mL of 0.3N sulfuric acid. I entered. The feed material is believed to represent waste from battery acid regeneration. 2. tf of OA After passing through L for 420 minutes, the feed contained 50 ppm Cd, 299 ppm Fe. m.

and 233 mL of 0.95N sulfuric acid containing 84 pp- of Ca. The product is Cd 3.47N sulfur containing 1.4ppm, 5.8ppm Fe and 4ppm Ca The acid was 36b+L.

Comparison box The same stack used in Example 1 was used, but in this case the bipolar membrane was replaced. Resistor 3 ohm ci manufactured in accordance with U.S. Pat. No. 4,738,764 reported a conventional electrodialysis device in the prior art using a cationic membrane with . Supplement The feed materials were Ca'''s 13Bppm, Fe'''450ppm and Cd''''9o. It was 170 mL of 8.76N sulfuric acid containing pps. Current to 2.5 for 430 minutes I passed it. The sulfuric acid in the final feed solution was 0.82N. products throughout the experiment was removed and refilled with water at a rate of 0.65-0.85 mL/min. of the solution taken out The analysis is given in Table 1.

Table 1 Time Fe Cd Ca HtSOa (minutes) (ppm) (ppm) (ppm) (N) 185 35 7 22 3.52 275 43 12 30 3.60 340 58 19 46 3.58 380 70 27 63 3.08 410 85 33 75 3.34 Average 57 19 52 Thus, acids produced by prior art processes have the same impurity to acid ratio. Even if it was the same, it was about 1/10 as pure.

Team Unie The impure acid to be purified is AI” 739pp+m, Fe43900ppm, M g″″130ppm+, Ca″420pp-.

Ni"" 40pp (Mn" 34ppm, Cu" 25pp- and Na 2 It was 1.268) INOs containing 600 ppm.

Such acids were thought to be waste products from the uranium extraction process.

Law Lord The apparatus and method of Example 1 was used to treat impure HNOs. To feed the electrode compartment 0.5N HNOs IL was used. Recirculation of impure acid through the stack was <300 wL/min. Concentrations of pure and impure acids observed during the experiment and The amounts and approximate current efficiencies are listed in Table 2. Isolation in the final pure acid product The purity was as follows: A1439.0ppm, Pe”1.7ppm, Mg” 0.2ppm, Ca” 1.0ppm, Ni” 0.7ppm.

Mu"　0.1ρps+ and Cu"　0. lppm* After the experiment, for membrane inspection The cell was disassembled. The anion membrane was as good as new.

Bipolar membranes contain a reddish-brown precipitate (probably Fe (041)) on their anionic faces. s), and this precipitate diffused into the cell. This precipitate is loose (sticky, H NOs (easily dissolved in P. The bipolar membrane showed no damage due to this precipitation. .

Chest-1-Front pure acid Time [H”] V obs V out’ Ac1d” Cue,’ Tack (min) (ml) (mL) (mL): L-eta Volt.

0.0. 20 250 0.0 − − −21.0. 59 252 5. 0. 872. 872 14.2058.0 1.26 260 5.0. 791. 817 13.50106.0 2.00 26B 5.0. 71 6. 770 13.30169.2 2.61 2B1 5.0. 527 ．． 678　13.3(1228,83,152925,0,537,64113 ,80279,63,532985,0,473,61015,30 impure acid Time [H4] νobs V out’ Ac1d Cue, stack ( minutes) (-9) (mL) (mL) Eff, Eta Volt.

0.0 1.26 1000 5.0 - - -24.5 1.15 986 5.0. 8B0. 880 14.1073.0. 95 963 5.0 ．． 70? , 761 13.4010g, 5. 80 947 5.0. 6 91. 737 13.30170.8. 55 922 5.0. 636 ．． 700 13.30230.6. 35 900 5.0. 509. 65 0 13.70262.5. 20 884 5.0. 688. 655 1 4.401, collected for analysis 2. Current efficiency at specific time intervals 1 Average current efficiency from the start of the experiment Group-mutual The experiment in Example 3 was repeated, but in this case it was thought that the acid was formed in the impure acid compartment. The current was interrupted for 2 minutes at half-hour intervals to allow time for the precipitate to redissolve.

This type of manipulation reduces the chance of cell occlusion and consequent damage to the bipolar membrane. It should be.

After the experiment, the cells were used for testing. There are traces of precipitate in the impure acid compartment. It was just a tad. The final pure acid is Pe 2.4ppm, Ca 1.6p pm and Al contained 1.7 ppm.

Kaya - Eiichimyo Imperial style 0.0. 22 249 0.0 - - 13.5830.0. 80 25 9 5.0. 892. 892 15.4360.0 1.32 263 5 ．． 0. 770. 829 14.8190.0 1.76 266 5.0 ．． 683. 779 14.66120.0 2.15 269 5.0. 6 43. 744 14.66150.0 2.50 271 5.0. 5B2 ．． 711 14.73180.0 2.86 275 5.0. 650. 701 14.85215.0 3.1? 276 5.0. 479. 66 4 15.20240.0 3.40 27? 5.0. 521. 649 15.53272.0 3.65 279 5.0. 479. 629 16 ．． 50 Fubimu Junji 0.0 1.24 1004 0.0 - -31.6 1.1.0 98B 5.0. 877. 87761.0. 99 974 5.0. 640. 75891.0. 85 959 5.0. 773. 763121.0. 70 944 5.0. 805. 774151.0. 60 930 5. 0. 534. 725181.0. 47 914 5.0. 671. 7 16215.0. 39 900 5.0. 361. 659241.0. 25 889 5.0. 784. 673261.0. 20 882 5. 0. 359. 648272.0. 15 871 0.0. 654. 6 49 doctor-1 The same experiment was carried out using the same equipment as in Example 3, but in this case the impure acid A high (>50 L/min) recirculation rate was used. The results of this experiment are listed in Table 4. Ru. After the experiment, the cell was disassembled and the membrane was inspected. Almost no precipitate exists in the cell , there was certainly much less precipitate than that observed in Example 3. Ta.

This demonstrates the importance of good flow to avoid precipitate formation in the cell. Demonstrate.

Section - Mutual table pure hydroxide 0.0. 20　396　5.0　-　-　-30.0　. 60 399 1. 0. 975. 975　16.4060.0　. 93 40B 20.0. 754. 858 15.5090.0 1.30 397 1.0. 832 ．． 849 15.10120.0 1.57 406 20.0. 657 ．． 800 14.90150.0 1.85 394 1.0. 654. 7 70 14.801B0.0 2.20 401 20.0. 837. 78 1 15.00210.0 2.43 389 1.0. 568. 750 15.20223.0 2.51 391 5.0. 492. 735 15 ．． 50 impure kasa-ni 0.0 1.25 1000 20.0 - -30.0 1.15 967 1.0. 663. 66360.0. 95 954 10.0 1.097 ．． 89090.0. 80 931 1.0. 815. 864120.0 ．． 65 917 10.0. 793. 846150.0. 54 894 1.0. 573. 7901B0.0. 40 880 10.0. 69 8. 775210.0. 25 857 1.0. 717. 766220 ．． 0. 22 B52 2.0. 359. 748223.0. 20 B5 0 0.0 1.139. 753 The final pure acid product contains the following metal impurities: Contained: Na, 90ppm, Fe, O, 8ppm.

Ca 0.8ppm, AI 0.4ppt Improved flow through the impure acid compartment This increase in purity was also the cause.

Comparative example l Recovery of acid from waste stainless steel pickling solution using the prior art equipment of Comparative Example 1 did. The waste (impure) acid is 0.41MFe” (23,OOOppm), 0.0 94M Ni'' (5500ppm), and 0.084M Cr'' (44 00 ppm). Furthermore, this waste liquid contains 2.33M F- and 1.2M F- Contained NO,-. Depending on the difference, the H' (free acid) i11 degree of the waste pickling solution is 1. It was 87M.

750 hL of waste pickling solution was used to feed the impure acid compartment and incubate for several days at 2.5 A. treated over a period of time. Fresh 0.1N HNOs 1752@L every day was placed in a pure (product) acid tank and removed the next day. Analysis and release of product acids Acid recovery was as follows: 1 Once on the table Batch Time HNOs HP Pe Ni Cr Free acid # (hour) mo le/L mole/L (ppm) (ppm) (ppm) Recovery% 1 2 4.0 2.57 0.29 591 766 185 182 26.0 2 ．． 48 0.25 745 1063 276 393 24.4 2.38 0.25 865 1515 394 584 18゜0 1.87 0.16 880 2049 495 72 Product acid can be recycled to the pickling operation. However, it contained high levels of metal impurities.

Spot once Using the apparatus shown in Figures 5 and 6 and described in Example 1, a stainless steel pickling process was carried out. The waste from the industry was disposed of. The waste (impure) acid is 0.32M Fe″’ (18,0 00ppm).

0.072M Ni'' (4200ppm) and 0.067M Cr'' (3500 ppm). Furthermore, the waste acid is 0.22M K′″, 1.1 It contained 6M No,- and 1.76M F-. Depending on the difference, the Ho of the pickling solution (Free acid) a degree was 1.4M. At the start, 1470 mL of waste pickling solution was impure. Pour 323 L of 0.5M HNOz into a pure acid tank. Ta. At the beginning of the experiment, the pure acid contained approximately 12 ppm Fe and 12 ppm Ni! 1 and Contained 3 ppm of Cr. A current of 2.5 A was passed through the cell for 6 hours. This acid The degree of 0 molar formation obtained by titrating sample 10d at 1 hour intervals was 1.45M and 2 after 1 hour. 2.1M after 3 hours, 2.75M after 3 hours, 3.25M after 4 hours, 3.25M after 5 hours It was 3.7 mice. The final amount of product was 335 mounds and 4.2 ON.

This was approximately 95 ppm of Fe, 20 ppm of Ni, and 9 ppm of (r). Based on the amount of pure acid product, 78% of the 'tIR acid was recovered. gold in the product The amount of genus impurities is about 1720 compared to Comparative Example 2.

The anionic surface of the bipolar membrane was covered by a fixed brown precipitate. long-term operation It is thought that the accumulation of such precipitates during production caused irreversible damage to the bipolar membrane. .

Flame-1 The apparatus was assembled as shown schematically in FIG. 0.0 in the anolyte and catholyte compartments. 5M KOH solution 11. was supplied. Place 90 hL of waste pickling solution in the section marked P. It was circulated to Waste (impure) acid is 0.35M Pe″5 (19,500pp++ ), 0.079M Ni” (4600pp@) and 0.089M Cr” (4 600 ppm). Furthermore, this waste acid is 0.25M K”, 1.18 It contained M NOs- and 1.88M P-. Depending on the difference, the H′″ of the pickling solution (Free acid) concentration was 1.36M. 0.5M 1 (N Ox 350*L was supplied. The section marked with P has FB 1.7pp1m. , 0.49M HNO33 containing CrO, 2pp- and Ni 0.2ppm A 30 mL charge and a t current of 2.5 A were passed for 4.0 hours. After the experiment, the free acid 86 % was recovered from the feed in the F compartment and the solution from the P compartment was 3.0ON HNO3. and 0.27N HF, Fe 12.9ppm, Cr 0.5ppm and N i　Oo-3pp was contained. By processing the solution in compartment A, additional pure acid is produced. was recovered. After the experiment, there was no sign of precipitation on the anionic side of the bipolar membrane. .

FIG, 2 34-A outside 36・ FIG.8 ,? Chaos L Turtle FIG.7 No CI/HCI Fe, 904/H2SO4 amendment translation submission form (Article 184-8 of the Patent Law) May 30, 1991

Claims (23)

[Claims] 1. at least one bipolar membrane consisting of a cationic layer and an anionic layer, each bipolar The polar membrane includes at least one first anion membrane and at least one second anion membrane. a feed material between the anion layer and the at least one first anion membrane; A device in which a compartment is present and a product compartment is present between the cationic layer and the second anionic membrane. from an aqueous feed stream containing an acid and a salt consisting of a septa ion and an anion. 1. A method for separating acids, comprising the steps of: adding an acid and gold to at least one feed compartment; providing an aqueous feed stream comprising: the process of supplying an aqueous product wave to at least one product compartment; A potential is applied to create a direct current and introduce H+ from the bipolar membrane into the product compartment. , transferring anions from the feed through an anion membrane to a product compartment; removing the resulting product from the product compartment; and removing the resulting feed stream from the product compartment; Process of removing from compartment A method consisting of 2. 2. The method of claim 1, wherein the device includes a plurality of alternating bipolar and anionic membranes. 3. The apparatus includes at least one feedstock compartment, each feedstock compartment producing one 2. The method of claim 1, alternating with object sections. 4. The apparatus further includes at least one anionic membrane between the anionic layer and the at least one anionic membrane. also contains one cationic membrane, with an acid compartment between the anionic layer and each cationic membrane. 2. The method according to claim 1. 5. The feed stream forms a complex with the anion layer or forms an insoluble hydroxide. 5. The method of claim 4, comprising metal ions. 6. Salts such as NaCl, HNaNO3, NH4Cl, Na2SO4, FeSO4, F e2(SO4)3, Ni(NO3)2, Cr(BF4)3, NH4NO3, Na Claims selected from the group consisting of 3PO4, CuSO4, KF and mixtures thereof The method described in Section 1. 7. Acid is acetic acid, HCl, H2SO4, HNO3, HBF4, HF, H3, PO4 and mixtures thereof. 8. The method according to claim 1, wherein the acid concentration is 0.1N to 5N. 9. 2. The method of claim 1, wherein the salt concentration is from 0.001 molar to saturation. 10. When the current is 25 to 300 amp. 2. The method of claim 1, wherein: /sq.ft. 11. The current is interrupted for 0.5 to 5 minutes at intervals of 15 minutes to 2 hours or substantially 2. The method of claim 1, wherein: 12. a linear flow velocity in at least one feedstock section of at least 2.5c; 2. The method according to claim 1, wherein the speed is m/sec. 13. at least two bipolar membranes, each bipolar membrane including a first bipolar membrane and a second bipolar membrane; The sexual membrane consists of a cationic layer and an anionic layer, with at least one anionic membrane and a few anionic membranes. Contains at least one cationic membrane, with an anionic membrane and a cationic membrane between two bipolar membranes. and an anionic membrane exists between the cationic layer and the cationic membrane of the first bipolar membrane. , a cationic membrane is present between the anionic layer and the anionic membrane of the second bipolar membrane, and the anionic membrane is An acid compartment exists between the anion layer and the septum ionic membrane, and an acid compartment exists between the anion membrane and the cation membrane. A device in which a feed compartment is present and a product compartment is present between the cation layer and the anion membrane. An aqueous feed stream containing an acid and a salt consisting of cations and anions is In the method of separating acid from providing an aqueous feed stream containing an acid and a metal cation to at least one feed compartment; supplying process; supplying an aqueous product stream to at least one product compartment; at least one acid compartment; the process of supplying an optionally acidic aqueous stream to the Flow is created to introduce H+ from the bipolar membrane into the product compartment and anion from the feed. transferring ions through an anionic membrane to the product compartment; removing the resulting product stream from the product compartment; removing the resulting acid stream from the acid compartment and removing the resulting feed stream from the feed compartment. 14. The feed stream can form complexes with the anionic layer or from insoluble hydroxides (f containing metal ions that can form rominsoluble hydroxides). 14. The method according to claim 13. 15. 2. The method of claim 1, wherein the acid in the product is neutralized with a base. 16. The base is NaOH, KOH, NH4OH, Ca(OH)2 or a mixture thereof. 16. The method of claim 15, wherein the method is selected from the group consisting of: 17. Next step: A process based on a two-compartment water separator for solutions containing salts and acids; , forming a first salt wave and a first acid stream; supplying the first salt stream to a three-compartment water splitter; and separating the first salt stream to form a second acid stream, a second base containing the base and optional salts; Forming a based stream and a dilute salt stream A method consisting of 18. 8. The method of claim 7, wherein the first salt stream has a pH of 3-7. 19. Claim 1 further comprising the step of purifying the first salt stream to remove heavy metal impurities. 7. The method described in 7. 20. 18. The method of claim 17, further comprising concentrating the dilute salt stream. 21. 18. The method of claim 17, wherein the dilute salt stream is concentrated by electrodialysis. 22. 18. The method of claim 17, wherein the dilute base is concentrated by reverse osmosis. 23. A three-compartment water separator includes an acid compartment, a base compartment, and a salt compartment, and separates the dilute salt stream from the base. 18. The method of claim 17, wherein the method is fed to a compartment.